When U.S. Secretary of State John Kerry addressed reporters on Saturday in Paris about military action against Syria, he tapped into a deep nerve in this country: the memory of two horrific world wars waged on French soil last century, when Americans came to France’s rescue, and in the case of World War I, when Germany launched the world’s first chemical attack in next-door Belgium in 1915. “What we are talking about is standing together and speaking with one voice,” Kerry said on Saturday evening in an impassioned plea, some of it in fluent French, which aired live on French TV networks. Standing with French Foreign Minister Laurent Fabius, Kerry — a Francophile with a grasp of European history — referred to Western Europe’s decision about whether or not to go to war against Adolf Hitler. “This is our Munich moment,” he said. “This is not the time to be silent spectators to slaughter.”

Kerry’s words were intended to sway people in Paris, a city which suffered under Nazi occupation and which narrowly averted widespread destruction during Hitler’s final days.

And yet, the plea to bomb Syrian President Bashar Assad’s forces appears to have little effect in shifting the opinion of regular French people — and might in fact be complicating President François Hollande’s efforts to win his citizens over to the idea.

The conundrum facing Western leaders is that as they press their case to bomb Assad’s military infrastructure, so public opinion appears to have hardened against the idea of military intervention — a withering rebuke to the efforts of Western policymakers since Assad’s alleged chemical attack on Aug. 21. “Since the attack, there is no doubt that the kind of momentum and backing for military action has unraveled,” says Anthony Dworkin, a senior policy fellow with the European Council on Foreign Relations in London. “Hollande to some degree is having the same problem as Obama: the more they make the case, the more unclear it becomes what [military action] is supposed to achieve and what the costs will be.”

For months, polls have shown growing opposition among the French for having their military join U.S.-led strikes against Syria. That is despite the overwhelming sympathy for the plight of Syrians, and a revulsion for the massacres depicted on the ground, which have aired regularly on French newscasts since the war began in March 2011. About 64% of French are against their country intervening militarily in the conflict, according to a survey conducted by the French polling company Ifop and published on Saturday in the center-right newspaper Le Figaro. That figure is up from 58% in an Ifop poll conducted last June, before the alleged chemical attack.

One reason for increasing wariness about military action is that France would now be Washington’s sole big Western partner in any bombing campaign. Polls suggest that French opinion hardened against military action after the British Parliament voted against intervention on Aug. 29. It seemed to swing further after Obama’s decision last week to wait for a vote in Congress, which is expected on Wednesday, according to Jérôme Fourquet, director of opinion for Ifop. “The French who are already hesitant are feeling more and more isolated,” Fourquet told TIME on Monday. “This is a real problem for François Hollande. He is at risk of alienating people by being the U.S.’s assistant.” As President, Hollande has the authority to order his military to act without approval from parliament. But as France’s isolation becomes more pronounced, lawmakers are pushing for a vote — which Hollande could well lose. And Obama’s continued push for military action could leave Hollande looking like he is simply doing Washington’s bidding, he says, adding, “France might appear to be submissive to the U.S., that we are following from behind.”

But there are other reasons why the French oppose military action. Hollande is in the minority on whether to intervene in Syria not only among his countrymen, but also, it seems, among the E.U.’s 28 leaders. Almost all oppose launching bombing strikes without approval from the U.N. Security Council — a nonstarter, since Assad’s close ally Russia has veto power there. German Chancellor Angela Merkel has made it clear she is against sending her military to support a U.S.-led bombing campaign. And Hollande has found little open support elsewhere in Europe. On Saturday, E.U. foreign ministers meeting in Lithuania said the chemical attack warranted a “clear and strong response” but failed to mention military strikes.

Alone on the continent, Hollande continues pressing the case for action against Assad, but has said he intends to wait for the report from U.N. inspectors, confirming the regime’s use of chemical weapons — a caveat that some analysts see as Hollande’s attempt to address French concerns. “An overwhelming proportion of French do not want to go to war, because they have a very negative view of the rebels,” says Karim Emile Bitar, senior fellow at the Institute for International and Strategic Relations in Paris. Bitar believes the widespread opposition to military action might have caught Hollande by surprise, since France’s military action in Libya in 2011 and in Mali earlier this year had strong support from most French people.

This time, winning popular backing seems an uphill battle, in part because many French politicians fear that Assad’s defeat could open the way for a Syria that might be worse for Western interests. “Both left-wing and right-wing politicians are very cautious about the rise of Islamic rebels,” Bitar says. “At this point, Hollande is pretty isolated, domestically and internationally.”